Full Answer
Browser-based pixels (Facebook Pixel, GA4 gtag, Google Ads tag) are JavaScript files loaded inside the visitor's browser. Ad blockers, Safari ITP, and privacy settings detect and block these scripts before they fire. Server-side tracking moves event processing to a server you control. When a WooCommerce purchase completes, your server sends the conversion data directly to platform APIs via authenticated server-to-server calls.
These requests originate from your server's IP address, not the visitor's browser, making them invisible to browser-level blocking tools. First-party deployment on your own subdomain (e.g., track.yourstore.com) adds a further advantage: requests appear to originate from your domain, bypassing both ad blockers and ITP's cross-origin cookie restrictions. The result is recovery of the 30-40% of conversion signals that client-side tracking loses to privacy tools.